Titanium oxide-containing material and process for preparing the same

ABSTRACT

A titanium oxide-containing material having a surface plated with titanium oxide. It is prepared by dissolving titanium fluoride (such as titanium tetrafluoride) in an amount of 2.0% owf in water, immersing a raw material in the obtained aqueous solution to treat the material with the aqueous solution at room temperature for 30 min, and adding a 0.5:1:1 (on a weight basis) mixture of boric acid, citric add, and DL-malic add in an amount of 0.5% owf to the aqueous solution to treat the material with the aqueous solution at 50° C. for 30 min, followed by washing with water. The raw materials usable herein include synthetic fibers, metals, glass, and woods, and may be in the form of sheet, plate, fiber, rod, or the like. Introduction of a noble metal, such as gold or silver, in addition to titanium oxide, onto the surface of the material enables the acceleration of the photocatalytic action of titanium oxide.

TECHNICAL FIELD

The present invention relates to a titanium oxide-containing substratethat has various functions such as deodorizing, stain resisting (stainproofing or stain releasing), and antibacterial functions because of thephoto-catalytic action of titanium oxide, and a process for preparingthe same.

BACKGROUND ART

Conventionally, it is known that titanium oxide has a photo-catalyticaction, by which it decomposes organic matters. The mechanism ofdecomposing organic matters by this photo-catalytic action is asfollows: When titanium oxide is irradiated with light such as visible orultraviolet rays, charge separation occurs, and electrons and highlyoxidizable electron holes are formed. The electron holes react withwater vapor or oxygen in air to form reaction active species such as OHradicals or O₂ ⁻, which decompose organic matters that are presentaround them instantly. At present, titanium oxygen is used forenvironmental clean-up of deodorizing, stain resisting, andantibacterial treatments etc. by utilizing its photo-catalytic action.

However, although adhesives have been used for attaching titanium oxideto materials such as metals, glass, wood, or the like, there has been aproblem that the adhesives are deteriorated by the photo-catalyticaction of titanium oxide, so that the attached titanium oxide is peeledoff. Furthermore, when titanium oxide is attached to a substrate formedfrom resins, synthetic fibers, or the like, it may be attached by mixingit in the substrate during the formation of the substrate, instead ofusing adhesives as mentioned above. It is herein noted that light suchas visible or ultraviolet rays is required for causing thephoto-catalytic action of titanium oxide, and moreover, it is necessarythat titanium oxide exists on the surface of the substrate so that itmay contact with an organic matter that is to be decomposed. However,according to the above-mentioned mixing method, it is difficult toattach titanium oxide on the surface of the substrate, and a largeamount of titanium oxide should be mixed in the substrate so thattitanium oxide may exist on the surface of the substrate in an amountrequired to develop various functions such as antibacterial,deodorizing, and stain resisting functions effectively. As a result,this method may affect properties of the substrate, and also isdisadvantageous in terms of cost performance. Furthermore, when thesubstrate is formed from organic matters such as synthetic fibers,resins, or the like, the portion at which titanium oxide is attached isdeteriorated, so that the titanium oxide may be peeled off.

Thus, it is an object of the present invention to provide a titaniumoxide-containing substrate in which various functions such asdeodorizing, stain resisting, and antibacterial functions due to thephoto-catalytic action of titanium oxide are displayed sufficiently, anda process for preparing the same, by developing an effective means forattaching titanium oxide to a surface of a substrate, in which peelingof titanium oxide is prevented.

DISCLOSURE OF INVENTION

In order to achieve the above object, the present invention provides atitanium oxide-containing substrate having a surface plated with ananatase type titanium oxide film, the film being adhered to the surfaceof the substrate without being burned.

Thus, when the substrate has a surface plated with titanium oxide, evenif the substrate is formed from organic matters, the portion at whichtitanium oxide is attached is not deteriorated by the photo-catalyticaction of titanium oxide.

Moreover, because the bonding strength of plating is large, titaniumoxide is not peeled off. Furthermore, because a surface of the substrateis plated with titanium oxide, the photo-catalytic action of titaniumoxide is displayed sufficiently, so that the substrate exhibits variousfunctions such as excellent deodorizing, stain resisting, andantibacterial functions.

In the present invention, the surface of the substrate may be coatedwith titanium oxide completely, or may be coated partially. It ispreferable that titanium oxide is attached to the surface of thesubstrate uniformly in a ratio of 1 to 10% (particularly a ratio of 2 to5%) on an area basis.

In the titanium oxide-containing substrate of the present invention, itis preferable that the substrate is at least one selected from the groupconsisting of synthetic fibers, glass, metals, resins, and wood.Moreover, the substrate also may be formed from proteins, cellulose, orthe like.

In the titanium oxide-containing substrate of the present invention, itis preferable that a noble metal is included in the titanium oxide film.This is because the photo-catalytic action of the titanium oxide isfurther accelerated by incorporating the noble metal, and also effectscharacteristic of the noble metal can be obtained. Furthermore, it ispreferable that the noble metal is incorporated by plating as in thecase of titanium oxide.

Furthermore, in the titanium oxide-containing substrate of the presentinvention, it is preferable that gold is included in the titanium oxidefilm, and a function of decomposing organic matters by oxidation isdeveloped even in the absence of light.

Moreover, in the present invention, the titanium oxide and the noblemetal in the substrate may be either ionic or non-ionic.

Next, the process for preparing the titanium oxide-containing substrateof the present invention comprises: adding a titanium fluoride in anaqueous solvent to prepare a solution; and bringing the solution intocontact with a surface of a substrate while adding boric acid, malicadd, and citric acid to the solution; whereby the surface of thesubstrate is plated with an anatase type titanium oxide film. It ispreferable that the pH of the solution in which boric acid, malic acid,and citric acid are added is in the range of 3 to 5.

In the process for preparing the titanium oxide-containing substrate ofthe present invention, it is preferable that titanium tetrafluoride isused as the titanium fluoride because of its excellent reactivity.

In the process for preparing the titanium oxide-containing substrate ofthe present invention, it is preferable that at least one selected fromthe group consisting of synthetic fibers, glass, metals, resins, andwood is used as the substrate. Moreover, other than these materials,those materials as mentioned above also may be employed.

Because of the same reasons as mentioned above, in the process forpreparing the titanium oxide-containing substrate of the presentinvention, it is preferable that a noble metal is incorporated in thetitanium oxide film.

Moreover, in the present invention, the “substrate” includes substratesafter being processed into products as well as substrates before beingprocessed into products. Furthermore, it also includes substrates formedon a surface of other objects, such as coating films.

BEST MODE FOR CARRYING OUT THE INVENTION

The titanium oxide-containing substrate of the present invention isprepared, for example, as follows. In the following, “% owf” representspercentage by weight to the weight of the substrate to be treated. Forexample, 5% owf of an additive in the case of treating 3 kg of substrateindicates 150 g of the additive.

First, a substrate to be treated is prepared. The materials as mentionedabove mentioned may be employed as this substrate. Furthermore, theshape of the substrate is not particularly limited, and it may be in theform of, e.g. fiber, plate, rod, or the like.

On the other hand, a titanium fluoride is added to an aqueous solvent toprepare a treating solution. Usually, water is used as the aqueoussolvent. Furthermore, other than the above-mentioned titaniumtetrafluoride, titanium trifluoride or the like also can be used as thetitanium fluoride. In this case, the ratio of the titanium fluoride isusually from 0.1 to 5% owf, preferably about 2.0% owf Moreover, bychanging this ratio, the ratio of the titanium oxide introduced into thesurface of the substrate can be adjusted.

Then, the treating solution is brought into contact with the surface ofthe substrate. When titanium oxide is introduced into a portion of thesurface of the substrate, only that portion may come into contact withthe solution. When titanium oxide is introduced into the entire surfaceof the substrate, the whole substrate may be immersed into the solution.Moreover, prior to this surface contacting treatment, it is preferablethat the surface of the substrate is washed with water sufficiently.

Next, boric acid, malic acid, and citric acid are added to the treatingsolution. By adding these adds, an anatase type titanium oxide film isformed on the surface of the substrate. Moreover, although an anatasetype titanium oxide film can be formed by adding only boric acid, byadding malic acid and citric acid as well, an anatase type titaniumoxide film that is dense and has good adhesion is formed. The degree ofadding the three types of acids is controlled so that the pH of thetreating solution becomes in the range of 3 to 5.

The above treatment is usually carried out under conditions at atemperature of 20 to 50° C. and for 30 to 60 minutes, preferably atabout 50° C. and for about 30 minutes.

When the surface of the substrate is plated with an anatase typetitanium oxide film by such a process, the titanium oxide is not peeledoff until the substrate is broken. Moreover, photo-catalytic reactiondoes not develop in a portion at which titanium oxide is attached to thesubstrate, but it develops at the interface between the titanium oxideexposed from the surface of the substrate and air, so that the strengthof the attachment is not reduced by the photo-catalytic action oftitanium oxide.

Thus, a titanium oxide-containing substrate is produced without using anadhesive or the like.

The ratio of the titanium oxide that is introduced onto the surface ofthe titanium oxide-containing substrate of the present invention isusually from 1 to 10%, preferably from 2 to 5% on an area basis.Furthermore, in the present invention, although the titanium oxide thatis introduced onto the surface of the substrate is usually titaniumdioxide, it also may be titanium monoxide or titanic trioxide.Furthermore, as a titanium dioxide, it is preferable to use ananatase-type that is excellent in photo-catalytic function. After beingwashed with water, the titanium oxide-containing substrate of thepresent invention can be processed into a desired product.

Furthermore, the method for introducing titanium oxide onto a surface ofa substrate according to the present invention can be applied to asubstrate that has been processed into a product. For example, it ispossible that a garment is produced by processing a synthetic fiber, andthe above-mentioned method of the present invention is applied to thisgarment. Furthermore, when a substrate that is formed from wood, metals,resins, or the like is coated with a paint, and the above-mentionedmethod of the present invention is applied thereto, the surface of thecoating film is plated with titanium oxide.

As mentioned above, in the present invention, it is preferable that anoble metal is included in the titanium oxide film. In the following,combinations of titanium oxide and noble metals are described.

Titanium Oxide and Gold

By attaching gold as gold ions to a surface of a substrate, thereactivity of active oxygen generated by the photo-catalytic action oftitanium oxide to organic matters can be increased. For example, whentitanium oxide and gold are attached to a surface of a substrate in theratio by weight of 1:0.001 of titanium oxide to gold, decomposition ofcontaminating organic matters such as tar of tobacco can be accelerated.Although the active oxygen generated by titanium oxide does not haveselectivity in its reaction, by introducing gold ions, the active oxygenis allowed to react selectively with harmful substances contained insmoke of tobacco, which are partially ionized. Moreover, the ratio byweight of titanium oxide to gold on the surface of the substrate isusually from 100 to 10,000:1, preferably from 1000 to 2000:1.

Titanium Oxide and Silver

In theory, titanium oxide does not develop its photo-catalytic actionwithout light. On the other hand, it is known that silver exhibitsantibacterial and deodorizing actions under a condition without lightand also exhibits almost no toxicity, so that it has been usedtraditionally as a material of antibacterial agents and deodorants.Thus, by attaching silver to a surface of a substrate in addition totitanium oxide, antibacterial and deodorizing properties are developedregardless to the presence or absence of light. Furthermore, because ofthe activity of silver, ozone can be produced using moisture and oxygenin the air, and thereby the photo-catalytic reaction of titanium oxidecan be further accelerated. Moreover, the ratio by weight of titaniumoxide to silver on the surface of the substrate is usually from 10 to100:1, preferably from 50 to 60:1.

Titanium Oxide and Zirconium

Zirconium ion is a highly active ion having a coordination number ofeight. By introducing zirconium ions onto a surface of a substrate alongwith titanium oxide, the photo-catalytic reaction of titanium oxide canbe accelerated. Moreover, the ratio by weight of titanium oxide tozirconium on the surface of the substrate is usually from 10 to 20:1,preferably 10:1.

Other than the above-mentioned combinations, a combination such as thatof titanium oxide, silica, and silver also may be employed. The commonthing in all of these combinations of titanium oxide and noble metals isthat the noble metals accelerate or stabilize the photo-catalytic actionof titanium oxide.

The noble metals can be introduced onto the surface of the substrate inaccordance with the method for introducing titanium oxide. That is, acompound of each noble metal is dissolved in water along with titaniumfluoride. Examples of the compound of noble metal include chloroauricacid, silver nitrate, and zirconium acetate. Moreover, the ratio of thecompound of a noble metal to be dissolved is adjusted so that the ratioof the noble metal on the surface of the substrate falls in theabove-mentioned range. Moreover, in the same way as the above, bybringing this solution into contact with a surface of a substrate whileadding boric acid, malic acid, and citric acid to the solution, titaniumoxide and a noble metal can be deposited (plated) on the surface of thesubstrate. Moreover, it is presumed that a noble metal (particularlygold) is absorbed between the molecules of titanium oxide during thedeposition.

In the following, examples of the present invention are described.

EXAMPLE 1

Titanium oxide was introduced into a synthetic fiber (type: polyesterfiber) according to the following procedure to produce a titaniumoxide-containing synthetic fiber.

First, titanium tetrafluoride was dissolved in water in an amount of2.0% owf. The synthetic fiber was immersed into this aqueous solution,and treated at room temperature for 30 minutes. Then, a mixture of boricacid:citric acid:D,L-malic add in the ratio by weight of 0.5:1:1 wasadded to the aqueous solution in an amount of 0.5% owf, and treated at50° C. for 30 minutes. At this time, the solution has a pH of 3. Then,it was washed with water, and a titanium oxide-containing syntheticfiber was obtained.

The thus obtained titanium oxide-containing synthetic fiber wasinvestigated for its antibacterial, deodorizing, and stain resistingproperties, and peeling degree of titanium oxide, according to themethods as follows.

Antibacterial Property

Antibacterial property was investigated by a Shake Flask methoddetermined by Association of Antibacterial Treatments for Textiles,Japan, SEK. The test strains used were Klebsiella pneumonise IFP13277and Staphylococcus aureus FDA 209P. Furthermore, as a control, thesame test was carried out for an untreated polyester fiber. Moreover,the numerical values in Table 1 below are the average of bacterialnumbers in three samples. Furthermore, in Table 1, the treated polyesterfiber indicates the titanium oxide-containing polyester fiber of Example1, and the untreated polyester fiber indicates a polyester fiber thathas not been subjected to the above-mentioned treatment. This alsoapplies to other tables.

TABLE 1 (Antibacterial Property) Right After After Shaking SterilizationName of Sample Preparation for 1 hour Rate (%) Name of Bacterium:Klebsiella pneumonise IFP 13277 Blank Test 1.90 × 10⁴ 1.97 × 10⁴ −3.7Untreated Polyester Fiber 1.90 × 10⁴ 1.60 × 10⁴ 15.8 Treated PolyesterFiber 1.90 × 10⁴ 50 99.7 Name of Bacterium: Staphylococcus aureus FDA209P Blank Test 1.64 × 10⁴ 1.75 × 10⁴ −6.7 Untreated Polyester Fiber1.64 × 10⁴ 1.32 × 10⁴ 19.5 Treated Polyester Fiber 1.64 × 10⁴ 20 99.9

Deodorizing Property

Deodorizing property was investigated by a teddler-pack (Tedler-bag)method. That is, a 3000 ml capacity teddler pack was charged withammonia, hydrogen sulfide, and acetic acid at predeterminedconcentrations, and further a sample was put therein, and the pack wassealed. The changes in the concentrations of the respective gases weremeasured at the initial time of the sealing, and at 5 minutes, 30minutes, and 60 minutes after the sealing by a gas-tech detector(gas-detecting tube). Moreover, the measurement was carried out underlight irradiation (10 centimeters below a 30 W fluorescent light).

TABLE 2 (Deodorizing Property) Under light irradiation: 10 centimetersbelow a 30 W fluorescent light Initial time 5 minutes 30 minutes 60minutes (ppm) (ppm) (ppm) (ppm) Ammonia 300 250 120 30 Hydrogen Sulfide30 25 10 5 Acetic Acid 100 70 40 10

Stain Resisting Property

One gram of an instant coffee (Registered Trademark: NESCAFE GOLD BLEND,manufactured by Nestlé Japan Limited) and 1 g of dark soy sauce wereadded into 100 ml of water to prepare an artificaial contaminatingliquid. A sample was immersed in this liquid, and then dried (Pad-Dry),so that a contaminated test sample was prepared. On the other hand, asample that has not been treated with titanium oxide was immersed in theartificial contaminating liquid, and then died, to prepare a control.These samples were placed 10 centimeters below a 36 W fluorescent light,and exposed to the light for 20 hours. After that, deodorization ratesof the samples were measured by a color-difference meter. And theinitial color of the samples and the color of the samples after beingexposed to the light for 20 hours were measured by a color-differencemeter. The results are shown in Table 3 below.

TABLE 3 (Stain Resisting Property) Under light irradiation: 10centimeters below a 30 W fluorescent light, after being exposed to thelight for 20 hours Initial Color Color after 20 hours UntreatedPolyester Fiber 100 85 Treated Polyester Fiber 100 52

Peeling Degree of Titanium Oxide

Peeling degree of titanium oxide was measured under the conditionsspecified in JIS L 0217 103 (method using a household electric washingmachine). That is, 50 g of a polyester fiber treated with titanium oxidewas prepared, and the amount of titanium oxide in the polyester fiberwas measured after 10 times and 20 times of washing. The amount oftitanium oxide was determined by burning the titanium oxide-treatedpolyester fiber in an electric furnace at 1000° C. and determining theweight of the residue (titanium oxide). Then, peeling degree of titaniumoxide was evaluated by a ratio (%) of the amount of titanium oxide afterwashing to the amount of titanium oxide before washing. The results areshown in Table 4 below. Moreover, in Table 4 the amount of titaniumoxide attached is expressed by a ratio (%) to the total 50 g of thetitanium oxide-treated polyester fiber.

TABLE 4 (Peeling Degree of Titanium Oxide) Amount of Titanium PeelingDegree Oxide Attached (%) (%) Initial time 0.52 — After 10 times ofwashing 0.51 1.9 After 20 times of washing 0.48 7.7

According to the results of the above Tables 1 to 4, it is understoodthat the polyester fiber in which titanium oxide is incorporated wasexcellent in antibacterial, deodorizing, and stain resisting properties,and also that the peeling degree of the incorporated titanium oxide wasextremely small.

EXAMPLE 2

Using stainless steel (20 cm²) in place of the polyester fiber, titaniumoxide was introduced onto the surface of she stainless steel by the sameprocess as in Example 1. This stainless steel was investigated for itsstain resisting and deodorizing properties according to the same methodsas the above. The results are shown in Tables 5 and 6 below. Moreover,in Table 6 below, the treated stainless steel indicates the titaniumoxide-containing stainless steel of Example 2, and the untreatedstainless steel indicates a stainless steel that has not been treatedwith titanium oxide.

TABLE 5 (Deodorizing Property) Under light irradiation: 10 centimetersbelow a 30 W fluorescent light Initial time 5 minutes 30 minutes 60minutes (ppm) (ppm) (ppm) (ppm) Ammonia 300 250 120 30 Hydrogen Sulfide30 25 10 5 Acetic Acid 100 70 40 10

TABLE 6 (Stain Resisting Property) Under light irradiation: 10centimeters below a 30 W fluorescent light, after being exposed to thelight for 20 hours Initial Color Color after 20 hours UntreatedStainless Steel 100 85 Treated Stainless Steel 100 52

According to the results of the above Tables 5 and 6, it is understoodthat the stainless steel treated with titanium oxide was excellent instain resisting and deodorizing properties. Furthermore, it also wasconfirmed that this stainless steel had an excellent antibacterialproperty, and also the peeling degree of titanium oxide was extremelysmall.

EXAMPLE 3

Using titanium oxide and gold, a polyester fiber was treated accordingto the following procedure. First, titanium ions were generated in asolution using titanium fluoride in the same way as the above.Furthermore, chloroauric acid (in the ratio by weight of 0.001 to thetitanium oxide) was added to this solution, so that gold ions weregenerated as well as titanium ions. Then, in the same way as in Example1, a mixture of boric acid, citric add, and D,L-malic acid (mixtureratio by weight of 0.5:1:1) was added into the solution. As a result,generated titanium oxide ions and gold ions are deposited on the surfaceof the polyester fiber, and bind to it strongly.

Then, the thus obtained polyester fiber treated with titanium oxide andgold was investigated for its antibacterial, deodorizing, and stainresisting properties by the above-mentioned methods. The results areshown in Tables 7, 8, and 9 below, respectively. Moreover, in thesetables, the treated polyester fiber (or treated) indicates the polyesterfiber treated with titanium oxide and gold of this example, and theuntreated polyester fiber (or untreated) indicates a polyester fiberthat has not been subjected to the above-mentioned treatment.

TABLE 7 (Antibacterial Property) Right After After Shaking SterilizationName of Sample Preparation for 1 hour Rate (%) Name of Bacterium:Klebsiella pneumonise IFP 13277 Untreated Polyester Fiber 1.90 × 10⁴1.97 × 10⁴ −6.4 Treated Polyester Fiber 1.90 × 10⁴ 50 99.7 Name ofBacterium: Staphylococcus aureus FDA 209P Untreated Polyester Fiber 1.64× 10⁴ 1.75 × 10⁴ −6.7 Treated Polyester Fiber 1.64 × 10⁴ 20 99.9

TABLE 8 (Stain Resisting Property) Under light irradiation: 10centimeters below a 30 W fluorescent light, after being exposed to thelight for 20 hours Initial Color Color after 20 hours UntreatedPolyester Fiber 100 85 Treated Polyester Fiber 100 22

TABLE 9 (Deodorizing Property) 5 30 60 Initial time minutes minutesminutes Under light irradiation: 10 centimeters below a 30 W fluorescentlight (ppm) Ammonia Untreated 300 280 240 200 Treated 300 150 20 0Hydrogen Sulfide Untreated 30 30 29 29 Treated 30 20 10 5 Acetic AcidUntreated 100 70 55 40 Treated 100 20 10 0 Under Darkness (ppm) AmmoniaUntreated 300 280 240 200 Treated 300 170 40 0 Hydrogen SulfideUntreated 30 30 29 29 Treated 30 20 9 0 Acetic Acid Untreated 100 70 5540 Treated 100 20 0 0

According to the results of the above Tables 7, 8, and 9. it isunderstood that the polyester fiber in which gold was incorporated aswell as titanium oxide was further excellent in antibacterial,deodorizing and stain resisting properties.

In addition, it was confirmed that peeling of titanium oxide and goldwas so extremely small in this polyester fiber. Moreover, in evaluatingthe deodorizing property, decomposition of gases such as ammonia alsowas tested under darkness, and surprisingly, it was confirmed that theorganic gases were decomposed even under darkness, i.e. under acondition without light such as visible or ultraviolet rays.

Example 4

Using stainless steel (20 cm²) in place of the polyester fiber, titaniumoxide and gold were introduced onto the surface of the stainless steelaccording to the same procedure as in Example 3. Then, this stainlesssteel was investigated for its deodorizing and stain resistingproperties by the above-mentioned methods. The results are shown inTables 10 and 11 below. In Table 11, the treated stainless steelindicates the stainless steel treated with titanium oxide and gold ofthis example, and the untreated stainless steel indicates stainlesssteel that has not been subjected to the above-mentioned treatment

TABLE 10 (Deodorizing Property) Under light irradiation: 10 centimetersbelow a 30 W fluorescent light Initial time 5 minutes 30 minutes 60minutes (ppm) (ppm) (ppm) (ppm) Ammonia 300 200 80 10 Hydrogen Sulfide30 15 5 0 Acetic Acid 100 40 10 0

TABLE 11 (Stain Resisting Property) Under light irradiation: 10centimeters below a 30 W fluorescent light, after being exposed to thelight for 20 hours Initial Color Color after 20 hours UntreatedStainless Steel 100 85 Treated Stainless Steel 100 30

According to the results of the above Tables 10 and 11, it is understoodthat the stainless steel on which gold was incorporated as well astitanium oxide was further excellent in deodorizing and stain resistingproperties. Furthermore, it was confirmed that peeling of titanium oxideand gold was extremely small in this stainless steel, and also anexcellent antibacterial property was observed.

INDUSTRIAL APPLICABILITY

As mentioned above, in the titanium oxide-containing substrate of thepresent invention, by plating a surface of the substrate with an anatasetype titanium oxide film, the anatase type titanium oxide film isattached to the surface without causing peeling. Therefore, the titaniumoxide-containing substrate of the present invention is provided withvarious functions such as antibacterial, deodorizing, and stainresisting functions because of the excellent photo-catalytic action oftitanium oxide. Furthermore, because titanium oxide developsphoto-atalytic action by absorbing light such as ultraviolet rays, thetitanium oxide-containing substrate of the present invention also has aneffect of inhibiting ultraviolet rays (so-called UV cut effect).Furthermore, in the titanium oxide-containing substrate of the presentinvention, because titanium oxide also has a masking effect, the basecolor of the substrate can be masked by controlling the incorporatingrate of titanium oxide. Moreover, a bright pure-white color can beattained using a titanium white, which is an excellent white pigment.Furthermore, by incorporating a noble metal in addition to titaniumoxide, the photo-catalytic function of titanium oxide can be furtherenhanced, and also various functions of the noble metal can be providedto the substrate.

What is claimed is:
 1. A process for plating a surface of a substratewith an anatase titanium oxide film, comprising: adding a titaniumfluoride in an aqueous solvent to prepare a solution; and bringing thesolution into contact with the surface of the substrate while addingboric acid, malic acid, and citric acid to the solution.
 2. The processof plating a surface of a substrate with an anatase titanium oxide filmaccording to claim 1, wherein the titanium fluoride is titaniumtetrafluoride.
 3. The process of plating a surface of a substrate withan anatase titanium oxide film according to claim 1, wherein thesubstrate is at least one selected from the group consisting ofsynthetic fibers, glass, metals, resins and wood.
 4. The process ofplating a surface of a substrate with an anatase titanium oxide filmaccording to claim 1, wherein a noble metal is incorporated in thetitanium oxide film.
 5. The process of plating a surface of a substratewith an anatase titanium oxide film according to claim 1, wherein a pHof the solution after boric acid, malic acid, and citric acid are addedis in the range of 3 to 5.